Hearing aids powered by a battery have been known for almost a century; see U.S. Pat. No 1,219,411 (Williams), for example. Modern technology has increased battery life greatly, yet it is annoying to have to replace batteries. Rechargeable batteries are a partial solution but require removal of the hearing aid and placement in a charger. Unless a user has two sets of hearing aids, the charging can be inconvenient.
Hearing aids having rechargeable batteries have been known in the art for a long time; e.g., see U.S. Pat. No. 3,297,933 (McCarthy). The trade-off between rechargeable batteries and non-rechargeable batteries is the inconvenience of having to replace the battery. There is also a trade-off in capacity. A non-rechargeable battery lasts much longer than a rechargeable battery having the same outside dimensions as the non-rechargeable battery.
Using light to recharge the battery in a hearing aid is disclosed in U.S. Pat. No. 5,210,804 (Schmid) and U.S. Pat. No. 5,253,300 (Knapp). In the Schmid patent, a photovoltaic cell is behind a semi-transparent door in a hearing aid. The cell does not recharge the battery during use. At night, the door is opened and the hearing aid is placed in a stand that shines light from lamps onto the photovoltaic cell. In the Knapp patent, the photovoltaic cell is external to the hearing aid, part of a recharging case. U.S. Pat. No. 5,303,305 (Raimo et al.) discloses a hearing aid powered by a secondary battery that is recharged by a photovoltaic cell on the hearing aid.
It is known in the art to control or program a hearing aid using radio frequency (RF) transmissions. It is also known in the art to transmit data to a hearing aid having a diode sensitive to infrared radiation; see U.S. Pat. No. 6,229,900 (Leenen). Remote controls for hearing aids are no less likely to be misplaced or need new batteries than remote controls for any other device. It is desired to eliminate the tedium of needing a remote control.